Quantum dots have unique physical and chemical properties and optical properties due to its special structure. In recent years, as a new type of fluorescent probe materials applied in chemical and biological analysis, medical diagnosis and other fields, quantum dots have become the focus of research. At present, some studies have been reported on the detection of heavy metal, veterinary drug and pesticide residues in food by using quantum dots as fluorescent probes. Related research reports showed that the use of quantum dots as a fluorescent probe to analyze the analyte with impact of food safety had advantages of high sensitivity, good selectivity, short response time, and less investment, which indicated the quantum dots as a fluorescent probe had wide application prospects in food safety inspection field. The malachite green had good antibacterial effect and low price, which was often illegally used in aquaculture as insecticides and fungicides. The malachite green had the potential carcinogenic effects, which was clearly listed in Chinese Food Animal Banned Veterinary Drugs and Compounds List in 2002, but in fact, malachite green residue has been detected in aquatic products breeding from time to time due to illegal addition. Malachite green residue detection method has been mainly reported, such as high performance liquid chromatography, surface enhanced Raman scattering spectroscopy, liquid chromatography-mass spectrometry (LC-MS), ultraviolet spectrometry, which were not easy to be applied and popularized at the basic unit, due to lower sensitivity, or longer single sample detection time, or expensive equipment, or complicated operation. Therefore, it was urgent to develop a detection method with high sensitivity, good selectivity, short response time and less input. Quantum dot fluorescent probe method in residue detection had the potential to meet the demand, but the current studies using the method of quantum dots to detect malachite green were rarely reported.
In view of this, based on the application prospects of residue detection by quantum dot fluorescent probe method in the field of food safety, the feasibility of detecting malachite green residue with illegal addition in aquaculture was researched in the present study by a water-soluble quantum dot fluorescent probe method, and the purpose was to establish a method to detect trace residues of malachite green in actual water and fish products.
In this study, water-soluble CdTe/ZnS quantum dot fluorescent probe was synthesized under mild conditions with 3-mercaptopropionic acid as a stabilizer. The main influence factors of water-soluble CdTe/ZnS quantum dot fluorescent probe to detect malachite green in the detection system were investigated, including buffer system type, buffer pH, buffer concentration, concentration of quantum dots, reaction time, concentration of malachite green, coexisting ions, etc. The best condition was obtained for the water-soluble CdTe/ZnS quantum dot probe method to detect malachite green on the basis of above investigation. Under the optimal detection condition, water-soluble CdTe/ZnS quantum dot fluorescent probe for quantitative detection of trace residues of malachite green was carried out in water and fish products. At the same time, the mechanism of water-soluble CdTe/ZnS quantum dot fluorescent probe method being used for the detection of trace residues of malachite green was studied by using ultraviolet-visible (UV-Vis) absorption spectroscopy and resonance light scattering technique.
As a result, a simple, rapid and sensitive approach to quantitative determination of illegally added malachite green residues in aquaculture was developed based on the fluorescence quenching of water-soluble CdTe/ZnS quantum dots by malachite green. Under the optimized conditions, i.e., pH=8.0, 0.065 mol/L Tris-HCl and 1.60×10^－4 mol/

Heavy metal contaminants enter the environment through various means, causing heavy metal pollution in the soil, especially heavy metals in farmland soils, which are becoming increasingly serious. Microorganisms, especially bacteria have a large surface area, are charged and have strong metabolic activity, and play a unique role in remediation of heavy metalcontaminated soil. The cadmium-tolerant strain m6, isolated from cadmium-polluted soil by our lab, has a strong ability to enhance the mobility and bioavailability of heavy metals in soils. Ordinary surfactants also can activate heavy metals and improve the migration and bioavailability of heavy metals in soils, and have a positive effect on the removal of heavy metals in contaminated soils and sediments. In our previous study, a heavy metal adsorbent Beiyang rod (BY rod) was set up, which can adsorb heavy metals including mercury, zinc, cadmium and copper in soils. Therefore, the objective of the present work was to study the remediation effect of cadmium-tolerant strains or surfactants combined with plant absorption and BY rod on soil heavy metal cadmium (Cd) pollution.
The BY rod combined with cadmium-tolerant bacteria m6 or surfactant was conducted in a field experiment, including CK, T1 (BY rod treatment), T2 (BY rod plus cadmium-tolerant bacteria treatment) and T3 [BY rod plus sodium dodecyl benzene sulfonate (SDBS) treatment]. Moreover, three species of hyperaccumulator (Sedum plumbizincicola, Sedum emarginatum Migo and Sedum alfredii) combined with cadmium-tolerant strain m6 (S1 treatment) or surfactant (S2 treatment) were set in a pot experiment. Both the field experiments and pot experiments were carried out in the greenhouses in Fuyang District, Zhejiang Province. The activities of soil urease, protease, phosphatase and dehydrogenase were measured by phenol-sodium hypochlorite colorimetric method, copper salt colorimetric method, triphenyltetrachloride azole (TTC) and benzodiazepine colorimetric method, respectively.
The results showed that the BY rod combined with cadmium-tolerant bacteria m6 or surfactant had higher absorption of the active cadmium than the control treatment. The cadmium-tolerant bacteria m6 and surfactants could significantly increase the content of available cadmium, enzyme activity and microbial quantity in the soil, while the effects as sodium dodecyl benzene sulfonate (SDBS) ＞ cadmium-tolerant bacteria m6. The reduction of the available cadmium concentration in the soil was the highest under the S. plumbizincicola treatment, and the absorbed concentrations of Cd and Zn in the S. plumbizincicola weresignificantly higher than those in the S. emarginatum and S. alfredii. After the potentially available cadmium in the soil was converted to activation state of cadmium, it could be absorbed by BY rod or cultivated plants. It was also revealed that the Cd concentration absorbed by S. plumbizincicola was higher than that by S. emarginatum and S. alfredii in the experiment of three kinds of sedum combined with cadmium-tolerant bacteria for remediation, and the soil enzyme activity and the abundance of microorganisms were higher after the remediation by S. plumbizincicola.
It is concluded that the combination of cadmium-tolerant bacteria and S. plumbizincicola is a feasible and effective remediation method for soil cadmium pollution.

Due to limited capacity of self-purification of water in ponds, accumulation of feed residue and metabolites lead toendogenous，exogenous pollution, and eutrophication. Currently, physical, chemical and biological methods are used to purifyaquacultural wastewater. Meanwhile，aquatic plants，aquatic animals and microorganism are used to purify water quality. Chinese mitten crab (Eriocheir sinensis) is an important economic aquatic crustacean in China; customarily, aquatic plants are often used to purify water quality during the breeding process of high?density cultured young crab. Alternanthera philoxeroides were planted in the pond, which could not only provide a habitat for shelter and moltforcrabs, but also purify the water quality. However, considering the low economic value of A. philoxeroides, some aquatic plants, which can produce high economic value and purify water quality, attracted attention of researchers. As we all know, rice?crab is a complex, efficient and ecological planting and breeding pattern. Meanwhile, reed type rice is lodging?resistant, which has tall stems and developed root system. However, high proportion of reed type rice will reduce the crab activity. space in the pond. Therefore, the present study was conducted to investigate the effects of reed type rice-planted area on water quality of crab pond, and provide some references for improving water quality in young crab pond.
Four treatments were conducted, including a control (group A), and three reed type rice?planted are as with 10% (group B), 20% (group C), 30% (group D), and every treatment had three replicates. Rice was planted around the pond, and transplanted floating aquatic plants (A. philoxeroides) in the middle of the pond, with bamboo piling fixed. Excess A. philoxeroides was removed periodically, which was controlled about 50% of the pond area. From July 2015 to October 2015, the water quality indicators including temperature, dissolved oxygen, pH, total hardness, permanganate index, total nitrogen, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, total phosphorus, phosphate phosphorus, chlorophyll a (Chl a)of the young crab pond were monitored. During the test, water samples were collected every 15 days in sunny and windless morning (8:00—9:30). Meanwhile, the determination of all water quality indicators was carried out using the procedure reported by Water and Wastewater Monitoring and Analysis Methods (fourth edition). Otherwise, water quality was evaluated according to Culture Area Fishery Water Quality Standard (GB 11607—1989) and Surface Water Quality Standard (GB 3838—2002).
The results indicated that the contents of nitrite nitrogen, total phosphorus and phosphate phosphorus in the reed type riceplanted crab pond were generally lower than those in the control group, while the contents of permanganate index and Chl a were higher than those of control. There were no significant differences of the other indexes between the treatment groups and control group. In the later stage of culture, the contents of permanganate index, ammonia nitrogen, nitrite nitrogen, phosphate phosphates and Chl a in the group D were higher than those in the group B and group C. While, the dissolved oxygen, total hardness and nitrate nitrogen content were the opposite. During the feeding period, the Chl a content in the group C was generally lower than that in the group B. Furthermore, the pH of water in the pond was in line with the fishery water quality and surface water environment standards, while the permanganate index, total phosphorus, ammonia nitrogen, total nitrogen reached class Ⅰ, Ⅱ, Ⅲ, Ⅳ of surface water environment standard, respectively.
In conclusion, reed type rice can purify the water quality in young crab pond, and the water quality is the best when 50% A. philoxeroides + 20% reed type rice are planted in young crab pond.